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Well distributed throughout Ireland, this common, crustose lichen occurs mostly on twigs, branches and fence timbers. It has crowded, rather swollen, yellow-green discs on a grey-green thallus that become distorted by the proximity of their neighbours. Frequently, the crowded discs become convex so losing their margins entirely and sometimes obscure the granular thallus. The disc edges are never powdery (sorediate). It grows always on acid-barked trees.

Key characteristics

The creamy-green discs spreading to exclude their margins and non-powdery edges distinguish it